[vte] build: Try to fix configure without vala installed

[Christian Persch <chpe src gnome org>]

commit 2d04ed4c5de05937022940c1d5ef0d4465b47595
Author: Christian Persch <chpe gnome org>
Date:   Sun Feb 12 20:10:06 2017 +0100

    build: Try to fix configure without vala installed

 configure.ac |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index 6dec53d..9ec4aac 100644
--- a/configure.ac
+++ b/configure.ac
@@ -380,7 +380,8 @@ m4_ifdef([VAPIGEN_CHECK],
   [VAPIGEN_CHECK([0.18])],
   [if test "$enable_vala" = "yes"; then
      AC_MSG_ERROR([[Vala requested but M4 macros not installed.]])
-   fi])
+   fi
+   AM_CONDITIONAL([ENABLE_VAPIGEN],[false])])
 
 # ****************
 # Test Application